This invention relates to a fluid pressure-operated, rapid shutoff extraction check valve for gas and steam turbines. The function of such a valve is to permit, by an automatic opening, steam transmission to the steam consumers after the pressure required by the steam consumers has been reached at the extraction point of the turbine and to protect the turboassembly during operation from disturbances originating in the consumer network.
The valve is to prevent impermissible temperature changes in the turbine caused by the backflowing steam, the condition of which differs from that at the extraction point of the turbine. A further function of the valve is to prevent the backflowing steam -- for example as a result of a condensate exhaust in feedwater preheaters upon pressure decrease -- from causing an impermissible rpm increase upon separation of the turbo-assembly from the network and to prevent water from being admitted to the turbine upon impermissible increase of the water level in the preheater.